At the time of SR, many top critics gave the movie a favorable reviews, some even praised Routh as Superman, I don't remember anyone criticizing Routh's performance.

But the fan community was divided, many found Routh's acting as wooden and lacklusture, I think that this may have been due to script which did not give him enough lines and the story which required Superman to look sad and serious most of the time coupled with the fact that there was little action in the movie.

But, Superman community was divided even before the movie was released, there were few people who were in the Tom Welling camp, to them nobody but Welling was suited for the role, then few were in the Chris Reeve camp who thought that there should be no more Superman movies as there could be no one who can fill in Chris Reeve's shoes.

Contrast this with Marvel fans who are united and support all Marvel Studios movies, regardless of the changes made to the source material.

Roger Ebert criticized the casting of Routh and said he lacked charisma. Ebert may be old but he is still one of the most influential critics.